What are the pimples on my labia minora?

I had small hard white head pimples on my labia minora for several years. They come out and then they go away. They are so hard that I can not squeeze them to pop it.
I have one that has grown larger than most and seems to be keep growing. I've shown doctors but the don't think it's a problem. I am concern because it been over A year and a half and it seems to keep growing.

Brief Answer:
Due to blocked gland.
Detailed Answer:
Hello,
Thanks for trusting us with your health concern.
The small hard white head pimples that you have on your labia minora is due to clogging up of the sebaceous glands that leads to formation of small lumps.
It can happen due to:
Moistness getting collected there
Presence of many oil secreting glands
Friction rub.
The increase in size of one of those is due to collection of secretions inside it. Since it is not painful infection is not likely.
Such pimples go away on their own. Since, it is symptomless, there is nothing to worry.
Squeezing or scratching these; shaving; wearing non cotton undergarments can aggravate these and may cause infection.
If the pimple is painful, it may be tense due to the pus collected inside. To ease this tension, try warm compress over it to soften the overlying skin. Slowly, the pimple would start draining.
As such it is benign and a harmless swelling. In case you are concerned regarding the size you can get it surgically removed after consulting your gynecologist.
Please feel free to discuss further. I will be glad to answer the follow up queries that you have.
Wishing you good health.
Regards.
Dr. Rakhi Tayal.
For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Rakhi-Tayal